The present invention relates to olefin polymerization catalyst compositions comprising a magnesium halide and a titanium halide and to a process for the polymerization of olefins using such catalyst compositions.
Numerous proposals are known from the prior art to provide olefin polymerization catalysts obtained by combining a component comprising magnesium halide and a titanium halide with an activating organoaluminum compound. The polymerization activity and the stereospecific performance of such compositions may be improved by incorporating an electron donor (Lewis base) into the component comprising titanium, into the organoaluminum activating component or into both these components. The catalyst compositions of this type which have been disclosed in the prior art are able to produce olefin polymers in an attractive high yield, calculated as g polymer/g titanium, and also with the required high level of stereoregular polymeric material.
The manufacture of magnesium halide supported catalysts for the polymerization of olefins by halogenating a magnesium alkoxide is well known. See U.S. Pat. Nos. 4,400,302 and 4,414,132 to Goodall et al. Since the morphology of the polymer is generally controlled by the morphology of the catalyst, much effort has been expended in attempting to control the morphology of such catalysts. Magnesium alkoxides have been formed by metathesis and/or have been all built to obtain the desired particle size, distribution and bulk density. These methods are costly and time consuming. Thus, there is a need for a simplified method for producing such catalysts but which still allows adequate morphology control.
The present invention provides a simplified means for morphology control for magnesium alkoxide catalyst particles. The magnesium alkoxide is simply formed in solution from a chemical reaction between a mixture of two or more alkyl or aryl magnesium compounds and any aldehyde or ketone. The use of mixed magnesium alkyls or aryls forms a mixture of magnesium alkoxides which is extremely soluble in organic solvents because of entropic effects. Others have prepared soluble magnesium alkoxide catalyst components by forming a complex of the magnesium alkoxide and a compound of another metal, such as aluminum, zinc or boron. U.S. Pat. Nos. 4,496,660; 4,496,661 and 4,526,943 disclose such complexes with other metal compounds. The present invention provides a soluble magnesium alkoxide catalyst component without the necessity of the addition of another metal compound to make it soluble.